Conventionally, a fuel tank is provided with a fuel tank valve that is a master valve type directly attached to the tank such that a fuel gas can be filled in the tank and can be output when the gas is used.
FIG. 6 is a cross-sectional view showing this type of fuel tank. Typically, a fuel tank 100 is formed in a substantially cylindrical shape and has a dual structure constituted by: a tank inner member 101 made of metal or the like and having high airtightness; and a tank outer member 102 made of a high tension material that is light in weight. A valve 103 is provided at one end of the tank 100, and the other end of the tank 100 is closed by a plug 104.
According to the structure shown in FIG. 6, in a case where a high-pressure fuel gas G is filled in the fuel tank 100 through the valve 103 attached to the tank 100, the temperature in the vicinity of a tank rear end that is directly hit by the jet flow of the fuel gas G increases. At the time of a high-pressure filling operation, the fuel tank 100 distorts by heat expansion caused by a partial temperature increase.
Here, as this type of conventional art, the fuel tank 100 shown in FIG. 7 is configured such that when filling the fuel tank 100 with the fuel gas G, the fuel gas G is diffused at an angle α through an ejection port 116 of an ejection port unit 115 provided at a valve 113, so that the distortion of the fuel tank 100 by the partial heat expansion is prevented (see PTL 1, for example).